In the field of electromagnetic radiation detection, it is well known how to use devices arranged in matrix form, that is comprising a plurality of juxtaposed elementary sensors in order to form a matrix having a number of lines and columns. The interactions of the electromagnetic radiations with these elementary sensors, also called “pixels,” generate flows of charge carriers, of which the energy and/or quantity corresponds to the energy of the incident radiation. Typically, the charge carriers consist of electrons or conduction gaps.
The charge carrier flux flows towards the read circuit associated with the sensor to form analog signals. These signals are then processed for subsequent reconstruction of a visible image, a function of the incident lighting.
An imager is thus produced, consisting of a matrix of pixels sensitive to a predefined range of electromagnetic radiations.
FIG. 1 shows the read circuit associated with an elementary detector in the infrared region, the said detector typically consisting of a photodiode, and using a MOSFET injection transistor.
In the present case, the photodiode dph 1 is subjected to a bias voltage via a voltage applied to the grid G of an injection transistor Minj 2, in the present case consisting of an N type MOSFET, connected to the photodiode dph 1 via its source S. The drain D of the injection transistor 2 is connected to an integration capacitance Cint 3.
When the photodiode 1 is subjected to a radiation with an energy hυ and fluxΦ, the said radiation causes the photodiode to generate a current i(Φ)) which passes through the injection transistor 2 by matching is voltage VGS, and also the integration capacitance Cint 3.
During the integration time T, the current i(Φ) charges the capacitance Cint with charge carriers according to the equation
            Qint      ⁡              (                  Φ          ,          T                )              =                  ∫        0        T            ⁢              i        ⁡                  (          Φ          )                      ,          ⁢            ⅆ      t        .  
A switch 4 serves to transfer the charge Qint((Φ,T) from the capacitance 3, for example to an amplifier for converting this charge to voltage, in a manner known per se.
It is obviously possible to use a P type MOSFET injection transistor, or even junction gate field effect transistors (JFET), and even bipolar transistors. These various transistors may be N or P doped, and may even be enriched or depleted.
If the incident photon flux is too intense, the current generated in the elementary detector rapidly becomes too high, and a depolarization of all the detectors of the matrix is observed. In such a situation, the matrix is then bloomed and the reconstruction of the visible image is compromised, or even impossible. In other words, the whole image becomes black even though a single, or even a few of the component pixels are affected by this blooming.
In order to overcome this malfunction, anti-blooming devices have been proposed, based on a clamping of the surplus current, but which does not prevent the saturation of the detector itself.
It is the object of the present invention to propose a detection device of the type in question, which overcomes these blooming problems, but without acting on the actual detector, but more on the electronic circuitry associated with the said detector, and therefore more particularly on the read circuit.